Treating oil wells



Patented Dec. 10, 1935 UNITED STATES TREATING OIL WELLS William V.Vietti and Allen D. Garrison, Houston, Tex., assignors to The TexasCompany, New York, N. Y., a corporation of Delaware No Drawing.Application August 11, 1934,

Serial No. 139,504

20 Claims. (01. 166-21) This invention relates to the treatment of anoil well, and more particularly to the chemical treatment of the sandadjacent a producing well in order to render the sand more permeable tocontinue to produce large amounts of water once an oil well startsmaking water.

It is an object of the present invention to treat a producing well whichis making water, so as to materially reduce the proportion of waterproduced, without substantially interfering with the flow of oil to thewell, and to accomplish this in a simple and expeditious manner.

It has heretofore been proposed to shut off the water in an oil well bythe use of cement by one of the following methods:

(1) Plugging oil the bottom of the hole by a cement plug,

(2) Bridging a hole and forcing cement back into the watered sand, laterdrilling out the cement and bridge; and

(3) Running a string of casing or a liner and cementing off upper water.is generally used in this work.

In accordance with the present invention, a well is treated bydepositing a chemical precipitate in the water wet sand adjacent thewell so as to render the sand less permeable to water and withoutsubstantially retarding the flow of oil to the well. It is found thatcertain types of precipitates act as preferential wetting agents torender a water wet sand more permeable to oil and less permeable towater. Thus, a sand which is completely wet by water and practicallyimpermeable to oil can be treated in place so that the sand then becomeswet by oil and the oil will flow quite readily through the treated sand.In the preferential wetting treatment, only a comparatively smallquantity of precipitate is required. This precipitate deposits on thesurface of the sand grains, and is believed to change their physicalcharacteristics, particularly wetting power, so that they becomepreferentially wet by oil rather than by water, assuming equal heads ofwater and oil.

In another embodiment of the invention, sufficient precipitate may bedeposited within the sand to partially block or cement the sand againstthe passage of water therethrough. If a chemical precipitate having apreferential wetting action of the character 1 11. Qescribed A Portlandcement above is employed, this will serve to effectively retard orreduce the proportion of water produced, while at the same time renderthe treated sand more permeable to oil such that even a larger flow or ahigher proportion of oil is produced through the partially blocked sand.

The process of the present invention may be conveniently carried out byfirst forcing into the well and into the sand adjacent the well asolution of a precipitatable chemical compound, 10 preferably of thepreferential wetting character described above. Then a solution of acompound which is active to react with the first mentioned compound topro'duce the desired precipitate is forced into the well and into thesand adjacent the bore of the well, so that these solutions come inreactive contact with each other when disseminated through the sandadjacent the well, with the result that the precipitate sol produced iseffectively distributed and deposited throughout the treated sand zone.The procedure described above may be repeated one or more times, so asto secure an effective deposit throughout the water wet sand.Preferably, this is then followed by forcing a charge of oil into thewell in order to force the chemicals farther out into the sandtoincrease the .zone of treatment, and to immediately create a zone ofsand around the well which is wet by oil.

Suitable materials which possess the preferential wetting propertyinclude various water and oil insoluble salts of sulphonated fats orfatty acids. For example, the heavy metal salts, in-

cluding those of calcium, barium, iron, mangapalmitic, oleic, and lowerfatty acids such as acetic, propionic and the like, are included. A verysatisfactory and comparatively cheap material, which is a by-product ofthe petroleum industry, is the sulphonic sludge acid derived from thetreating of petroleum oil with sulphuric acid. These various materialsmay be conveniently employed inthe form of their water soluble alkalimetal salts, whereby a solution of the soluble salt may be first forcedinto the bore of the well and intd the sand immediately surrounding thewell. Then, a solution of a water soluble calcium, barium or other heavymetal salt, such as a chloride, nitrate or other soluble salt of theheavy metals, is forced into the well and into the sand 5 to react wtihthe first mentioned solution to produce a precipitate of the heavy metalsalt of the sulphonated fat or fatty acid. For purposes of description,the salts of calcium, barium, and other alkaline earth metals, areincluded under the expression "heavy metal salt", along with the saltsof such metals as iron, manganese and the like which are more generallyunderstood as heavy metals. For economical reasons, calcium chloride ispreferred for this purpose, inasmuch as it constitutes a cheap andreadily available material which is frequently produced as a byproductin connection with oil and salt production.

As a specific example of the present invention, the following ismentioned. A dilute water solution of the sodium salt of the sulphonicsludge acids produced in the treatment of petroleum oil with sulphuricacid, is first forced through the sand; and this is followed by a washwith a dilute solution of calcium chloride. The result of these twowashes is that the calcium sulphonic sludge salt is precipitated on thesand grains. Another charge of the sodium salt is then forced into thewell, followed by another charge of the calcium chloride solution. Thismay be repeated still a third time, or even more, depending upon theextent of sand to be treated and the quantity of precipitate desired.Finally, a quantity of oil is pumped into the well which will force thechemicals farther out into the sand, and will render the sand in theimmediate vicinity of the well wet by oil.

This treatment results in the sand around the well being more readilywet by oil than by water. It does not constitute a complete block orcementing of the sand against the passage of water, but rather rendersit easier for the oil to come through the sand while the flow of wateris retarded. Oil which is present in the sands near the well will thenhave a freer passage to the well bore than it had before treatment. Inaddition, this treatment will produce in effect an enlarged screen,composed of sand, wet or preferentially wettable by oil, which the oilcan enter on its way to the surface.

We are aware that it has heretofore been the practice to flood an oilsand by the introduction of water and/or chemicals in one well, so thatthe water and/or chemicals will flood from this input well toward otherproducing wells, whereby oil is driven to the latter, although the inputwell is thereby flooded and rendered inactive. The present invention isdistinguished from this practice in that the producing well itself istreated by a controlled deposit of a water and oil insoluble precipitatewithin the sand immediately adjacent this producing well. Furthermore,the precipitate is of such character as to render the sandpreferentially wettable by oil, instead of flooding out any oil whichmay be present therein.

In accordance with the present invention highly permeable water wetsands can be partially plugged or cemented by forcing in relatively highconcentrations of chemicals, or large amounts of dilute solutions, ofchemicals. The heavy metal salts thus precipitated will then hinderpassage of fluids back through the highly permeable zones and will thusresult in partially blocking or cementing them. A material which acts asa preferential wetting agent is particularly suitable for this purpose,because it results in decreasing the water percentage while at the sametime rendering the sand more permeable to oil so that the oil productionmay be even increased, notwithstanding the partial block.

In addition to the chemicals enumerated above which may be employed topartially block or cement a sand of this character, other materials maybe employed. For example, an alkaline solution of the amphoterichydroxides, such as aluminum hydroxide, may be forced into the well, andupon dilution with water produce a water insoluble precipitate. This mayoccur by reaction with the water or chemicals naturally oc- 5 curring inthe well. Various other salt solutions, such for example as calcium ormagnesium chlorides or nitrates, may be used, which will react with theminerals in the well waters to form insoluble precipitates,- such assulphates, carbon- 10 ates, etc. of the specified metals. Compoundswhich are precipitated by dilution with water or aqueous metal saltsolutions naturally occurring in a well, will thus automatically beprecipitated in the water wet zones of the sand, without any 15substantial precipitation in or retardation of the flow of oil throughoil sand zones. This eliminates the necessity for any preliminarydetermination of the location of the water wet zones, which may be verydifficult. Any excess of the go solution pumped into the well is bailedout before pumping is resumed.

0bviously many modifications and variations of the invention, ashereinbefore set forth, may be made without departing from the spiritand scope 25 thereof, and therefore only such limitations should beimposed as are indicated in the ap pended claims.

We claim:

1. The method of treating an oil well to in- 30 crease the proportion ofoil and decrease the proportion of water produced therefrom, whichcomprises depositing in a water wet sand adjacent the well a chemicalprecipitate which acts to render the sand less permeable to water with-35 out substantially retarding the flow of oil to the well.

2. The method of treating an oil well, which comprises depositing in thesand adjacent the well a chemical precipitate which acts as a pref- 40erential wetting agent to render the sand more permeable to oil and lesspermeable to water.

3. The method of treating anoil well to increase the proportion of oiland decrease the proportion of water produced therefrom, which 5comprises depositing in a permeable water wet sand adjacent the well achemical precipitate in such quantity as to partially block thepermeable sand to the passage of water, without substantially retardingthe flow of oil to the well. 5

4. The method of treating an oil well, which comprises forcing into thewell and into a water wet sand adjacent the well a solution of aprecipitatable chemical compound, and reacting the chemical compound insitu within the sand to 55 effect a precipitation of the reactionproduct within the sand to render the latter less permeable to waterwithout substantially retarding the flow of oil to the well.

5. The method of treating an oil well, which 5 comprises forcing intothe well and into a water wet sand adjacent the well a solution of achemical compound which is precipitatable by metal salts, and thenforcing into the well and sand adjacent the well a solution of a metalsalt to 5 react with the said compound to cause precipitation of areaction product within the sand to render the latter less permeable towater without substantially retarding the flow of oil to the well.

6. The method of treating an oil well to in- 70 crease the proportion ofoil and decrease the proportion of water produced therefrom, whichcomprises forcing into the well and into a water wet sand adjacent thewell a solution of a chemical compound which reacts upon contact with 75the water and metal salts present in the sand to cause a precipitationof a reaction product within the sand to render the latter lesspermeable to water without substantially retarding the flow of oil tothe well.

7. The method of treating an oil well, which comprises depositing in thesand adjacent the well a precipitate of a water and oil insoluble saltof a sulphonated compound selected from the group consisting of fats andfatty acids.

8. The method of treating an oil well, which comprises depositing in thesand adjacent the well a precipitate of a sulphonated sludge derivedfrom the treating of petroleum oil with sulphuric acid.

9. The method of treating an oil well. which comprises depositing in thesand adjacent the well a precipitate of a heavy metal salt of asulphonic acid derived from the treating of petroleum oil with sulphuricacid.

10. The method of treating an oil well, which comprises depositing inthe sand adjacent the well a precipitate of a calcium sludge sulphonatederived by precipitating with a calcium salt a sulphonic sludge acidresulting from the treatment of petroleum oil with sulphuric acid.

11. The method of treating an oil well to improve the production of oilfrom the well, which comprises forcing into the well and into the sandadjacent the well a solution of a precipitatable compound which ispreferentially wettable by oil,-

then forcing into the well and into the said sand a solution to effectprecipitation of the said compound in the sand in an amount to not morethan partially block or cement the said sand, and finally forcing intothe well a charge of petroleum oil to force the solutions farther outinto the sand to increase the zone of treatment and to produce a zone ofat least partially permeable sand around the well which is wet by oil.

12. The method of treating an oil well to improve the production of oilfrom the well, which comprises forcing into the well and into the sandadjacent the well a solution of a precipitatable compound which ispreferentially wettable by oil, then forcing into the well and into thesaid sand a solution to effect precipitation of the said compound in thesand to render the sand preferentially wettable by oil, repeating theabove steps in the order named, the amount of said compound soprecipitated being insufficient to block or cement the sand, and finallyforcing into the well a charge of petroleum oil to force the solutionsfarther out into the sand to increase the zone of treatment and tocreate a zone of at least partially permeable sand around the well whichis wet by oil.

13. The method of treating an oil well, which comprises forcing into thewell a solution of a compound selected from the group consisting ofsulphonated fats and fatty acids and soluble salts thereof, followed byforcing into the well a solution of a metal salt of a character toeffect precipitation of the metal salt of the said compound within thesand adjacent the well. g

14. The method of treatingan oil well, which comprises forcing into thewell and into the sand adjacent the well a water solution of a solublecompound of a sulphonated sludge derived from the treating of petroleumoil with sulphuric acid, followed by forcing into the well and into thesand adjacent the well a solution of'a metal salt of a character toeflect precipitation of the metal salt of the sulphonated sludge withinthe sand adjacent the well. 4

15. The method of treating an oil well, which comprises forcing into thewell and into the sand adjacent the well a water solution of an alkalimetal salt of a-sulphonic sludge acid derived from the treating ofpetroleum oil with sulphuric acid, 5 followed by forcing into the welland into the sand adjacent the well a solution of a heavy metal saltactive to effect precipitation of the 1 heavy metal salt of thesulphonic sludge acid within the sand adjacent the well. 10 16. Themethod .of treating an oil well, which comprises forcing into the welland into the sand adjacent the well a water solution of a sodium salt ofa sulphonlc' sludge acid derived from the treating of petroleum oil withsulphuric acid, 15

followed by forcing into the well and into the sand adiacent the well awater solution of a soluble calcium salt active to effect precipita tionof the calcium salt of the sulphonic sludge acid within the'sandadjacent the well.

17. The method of treating an oil well, which comprises forcing into thewell a solution of a compound selected from the group .consisting' ofsulphonated fats and fatty acids and soluble salts thereof, followed byforcing into the we 35 a solution of a metal salt of a character toeffect precipitation of' the metal salt of the said compound within thesand adjacentthe well, and finally forcing into the well a charge ofpetroleum oil to force the chemicals farther out into 30' the saidsulphonic sludge acid within the sand adjacent the well, and finallyforcing into the well a charge of petroleum oil to force the chemicalsfarther out into the sand to increase the zone of treatment and tocreate a zone of sand (5 around the well which is wet by oil.

19. The method of treating an oil well, which comprises forcing into thewell and into the sand adjacent the well a water solution of a sodiumsalt of a sulphonic sludge acid derived from the treating of petroleumoil with sulphin'ic acid, followed by forcing into the well and into thesand adjacent the well a water solution of a soluble calcium salt"activeto effect precipitation of the calcium salt of the sulphonic sludge 5acid within the sand adjacent the well, and finally forcing into thewell a charge of petroleum oil to force the chemicals farther out intothe sand to increase the acne of treatment andtocreateaaon'eofsandaroundthewellwhich is wet by oil.

20.The method of treating an oil well which has a highly permeable waterwet sand adjacent thewellinordertoincreasetheproportionofoil anddecrease the proportion of water produced 55 therefrom, which comprisesdepositing in the said water wet sand a sufiiicent quantity of achemical precipitate .to partially block or cement thesaidwaterwetsanmthesaidprecipitatebeing :ofacharactertoactasapreferential,wetting agent to render the resultant partiallyblocked sandmorepermeabletooilandlesspenaeable towater. 4 v

. willful-WITH.

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